Zombiesmash style drag and throw required in 2D

I need your help friends. I am creating a game in which i have to gameObjects are running in to the scene and they are stealing another gameobject (scoring item) and run back to where they had came from. I have to drag them and throw them away so that they can't reach the score items. I have been able to drag and throw but they look too much heavy. It takes too much effort to drag them and throw them. Please suggest me how can i make them launch seamlessly similar to zombiesmash game. I want to use Raycast approach for it but Raycasting mess up the dragging part of the game. Following is my code for it.

Code (CSharp):

1.  
2. void Update ()
3.         {  
4.              
5.                 if (!isFalling) {      
6.                                 if (!isFoodPicked) {
7.                                         Run (true, gameObject);
8.                                 } else {
9.                                         Run (false, gameObject);
10.                                 }
11.                         }
12.          }
13.              
14. public void Run (bool inScene, GameObject target)
15.         {
16.                 if (inScene) {
17.                         RunIn (target);
18.                 } else {
19.                         Runout (target);
20.                 }
21.         }
22. private void RunIn (GameObject target)
23.         {  
24.                 target.rigidbody2D.velocity = new Vector2 (rigidbody2D.transform.localScale.x * -1, 0) * speed;
25.                 target.transform.localScale = new Vector3 (1.5f, 1.5f, 1.5f);
26.         }
27.      
28.      
29.         private void Runout (GameObject target)
30.         {
31.                 rigidbody2D.velocity = new Vector2 (rigidbody2D.transform.localScale.x, 0) * -speed;
32.                 transform.localScale = new Vector3 (-1.5f, 1.5f, 1.5f);
33.                 if (target) {
34.                        //move the stealing item with them
35.                         target.rigidbody2D.velocity = new Vector2 (rigidbody2D.transform.localScale.x, 0) * -speed;
36.                      
37.                 }
38.         }
39.  
40. void OnMouseDown ()
41.         {
42.                 startTime = Time.time;            
43.                 pickStartPos = transform.position;
44.             isFalling = true;
45.                 screenPoint = Camera.main.WorldToScreenPoint (gameObject.transform.position);
46.                 offset = gameObject.transform.position - Camera.main.ScreenToWorldPoint (new Vector3 (Input.mousePosition.x, Input.mousePosition.y, screenPoint.z));
47.              
48.                 rigidbody2D.isKinematic = true;
49.            
50.         }
51. void OnMouseDrag ()
52.         {
53.                 Vector3 curScreenPoint = new Vector3 (Input.mousePosition.x, Input.mousePosition.y, screenPoint.z);        
54.                 Vector3 curPosition = Camera.main.ScreenToWorldPoint (curScreenPoint), offset;
55.                 ;      
56.                 transform.position = curPosition;
57.                 anim = gameObject.GetComponent<Animator> ();
58.                 if (anim) {
59.                         anim.SetInteger ("Animstat", animStatDrag);
60.                 }
61.          
62. void OnMouseUp ()
63.         {
64.                 Debug.Log ("Mouse UP is Hit");
65.                 rigidbody2D.isKinematic = false;
66.                 rigidbody2D.gravityScale= 10;
67.                 pickThrowpos = transform.position;
68.              
69.                 force =  pickThrowpos- pickStartPos;    
70.              
71.              
72.                 if (Mathf.Abs (pickStartPos.x) != Mathf.Abs (pickThrowpos.x)) {
73.                         isThrown = true;
74.                         if (Mathf.Abs (pickStartPos.x) > Mathf.Abs (pickThrowpos.x)) {
75.                          
76.                         }
77.                 }
78.                 if (isThrown) {
79.                  
80.                         rigidbody2D.velocity = force * speed;
81.                      
82.                         anim = gameObject.GetComponent<Animator> ();
83.                         if (anim)
84.                         {
85.                                 anim.SetInteger ("Animstat", animStatDrop);
86.                         }
87.  
88.                 }
89.         }
90.  
91.         }
92.